1. Field of the Invention
The present invention relates to an electron emitting device, an electron source having a plurality of the electron emitting devices, an image forming apparatus such as a display device or an exposure device constituted by using the electron device, and a method for manufacturing them.
2. Related Background Art
An electron emitting device, e.g., a surface conduction electron emitting device utilizes a phenomenon such that an electric current is caused to flow through a conductive thin film formed on an insulating substrate in parallel to the film surface to produce the electron emission.
As a typical structural example of the surface conduction electron emitting device, there is one having a structure in which an electron emitting section is formed on a conductive thin film such as a metal oxide communicating between a pair of device electrodes provided on an insulating substrate by previously performing an electric process called forming. The forming is a process by which a voltage is usually applied to the both ends of the conductive thin film and the conductive thin film is locally fractured, deformed or transformed to change the structure so that an electron emitting section having an electrically high resistance is formed. The electron is emitted in the vicinity of a crack generated in the electron emitting section by applying a voltage to the conductive thin film to which the electron emitting section is formed to cause a flow of an electric current.
Since the surface conduction electron emitting device has a simple structure and can be easily manufactured, a plurality of the surface conduction electron emitting devices can be advantageously arranged and formed in a large area. Therefore, various applications for exploiting this characteristic have been studied. For example, there is an application to a charged beam source or an image forming apparatus such as a display device.
In particular, the display device can be a planar display device similar to a display device using a liquid crystal, and there is proposed a display device in which an electron source having a plurality of the surface conduction electron emitting devices arranged therein is combined with a fluorescent material for emitting a visible light ray by irradiation of an electron ray from the electron source as a spontaneous light type display device requiring no back light (specification of U.S. Pat. No. 5,066,883).
In regard to forming when a plurality of the devices are arranged to obtain the electron source and the image forming apparatus, there is proposed a hydrogen assist forming method by which a plurality of the devices on the same wiring are simultaneously and uniformly formed by flowing an electric current to the conductive thin film as a metal oxide film while inducing hydrogen (Japanese Patent Application Laid-Open No. 6-12997).
Further, there is proposed a forming method using a local reaction in which opposed device electrodes are made of different electrode materials and the electron emitting section is formed to an edge of one electrode of the conductive thin film extending between the device electrodes by using a material which reacts to the electrode material on the edge of one electrode below a given temperature (Japanese Patent Application Laid-Open No. 8-162002). In the embodiment of this publication, Pd and PdO are used for the conductive thin film; Au is used for the electrode which reacts to the conductive thin film; and Pt and Ni are used for the electrode which does not react.
In case of the surface conduction electron emitting device in which the electron emitting section is formed to a part of the conductive thin film by the above-described forming process, the power required for forming or an aspect and others of the electron emitting section largely vary depending on the film quality of the conductive thin film.
As to the forming power, in case of the electron source in which a plurality of surface conduction electron emitting devices are arranged and formed, a large electric current required for forming one device makes it difficult to simultaneously conduct electricity to a plurality of the surface conduction electron emitting devices to perform forming, and the large power needs an expensive forming apparatus and an increase in current capacity for the wiring, thereby requiring use of an expensive wiring material having the high electrical conductivity.
In addition, when manufacturing the above-described display device by combining the electron source in which a large number of the surface conduction electron emitting devices are arranged and formed with an image forming material and others, a high-temperature heating process must be carried out for multiple times in case of the display device using glass in particular. When such a high-temperature heating process is performed, the electric property of the conductive thin film may be changed and a desired voltage can not be applied to the electron emitting section in some cases.
More specifically, although a change in morphology during the above-described high-temperature heating process and a change in shape of a crack generated due to concentration of an electric current to the electron emitting section formed by the forming can be suppressed by using the conductive thin film having a high fusing point, employment of a metal having a high fusing point requires a large power during the forming as described above. On the other hand, the above-mentioned changes can be suppressed by using the metal oxide film for increasing a fusing point, but an electric current effectively flowing through the electron emitting section disadvantageously becomes small because the electric resistivity becomes incommensurably larger than that in case of using a metal.
Incidentally, according to the forming method using the local reaction proposed in Japanese Patent Application Laid-Open No. 8-162002, improvement of the device uniformity by controlling a shape of the electron emitting section and reduction in the forming current can be achieved, but the heat resisting stability after forming is not satisfactory.
It is an object of the present invention to provide an electron emitting device having a stable electron emitting characteristic and an electron source.
It is another object of the present invention to provide an electron emitting device having a stable electron emitting characteristic to heat in particular and an electron source.
It is still another object of the present invention to provide an image forming apparatus in which changes in image to be formed with time are reduced.
It is yet another object of the present invention to provide a method for manufacturing an electron emitting device, an electron source and an image forming apparatus, by which the electric power in the electric process is reduced as much as possible in the manufacturing process.
It is a further object of the present invention to provide a method for manufacturing an electron emitting device, an electron source and an image forming apparatus superior in characteristic reproducibility.
The present invention provides an electron emitting device provided with a conductive film having an electron emitting section between a pair of device electrodes, wherein the conductive film is made of a metal alloy.
Further, the present invention provides an electron emitting device provided with a pair of conductive films which are connected to each of a pair of device electrodes between the pair of device electrodes and arranged with a first gap therebetween, wherein the pair of conductive films are made of a metal alloy.
Furthermore, the electron emitting device is also characterized in that the metal alloy is an alloy composed of Pd and Pt or the conductive film contains a carbon film.
In addition, the present invention provides an electron emitting device provided with a conductive film having an electron emitting section between a pair of device electrodes, wherein the conductive film includes at least two types of all solid soluble metal.
Moreover, the present invention provides an electron emitting device provided with a pair of conductive films which are connected to each of a pair of device electrodes between the pair of device electrodes and arranged with a first gap therebetween, wherein the pair of conductive films include at least two types of all solid soluble metal.
Further, the electron emitting device is characterized in that the two types of metal are Pd and Pt or that a carbon film so arranged as to form a second gap narrower than the first gap is provided on the pair of conductive films and in the first gap.
Furthermore, the present invention provides an electron source having a plurality of electron emitting devices, wherein the electron emitting device is any one of the above-described electron emitting devices.
In addition, the present invention provides an electron source having a plurality of electron emitting devices matrix-wired on a substrate, wherein the electron emitting device is any one of the above-mentioned electron emitting devices.
Additionally, the present invention provides an image forming apparatus comprising an electron source and an image forming member for forming an image by irradiation of an electron ray from the electron source, wherein the electron source is any one of the above-described electron sources.
Moreover, the present invention provides a method for manufacturing an electron emitting device provided with a conductive film having an electron emitting section between a pair of device electrodes, the method for manufacturing an electron device comprising the steps of: forming the conductive film having at least two types of metal elements capable of forming a metal alloy; and applying a voltage to the conductive film.
Further, the present invention provides a method for manufacturing an electron emitting device provided with a conductive film having an electron emitting section between a pair of device electrodes, the method for manufacturing an electron emitting device comprising the steps of: forming the conductive film having at least two types of all solid soluble metal elements; and applying a voltage to the conductive film.
Furthermore, the above-described method for manufacturing an electron emitting device is characterized in that one of the two types of metal elements exists as a metal oxide and the other exists as a metal in the conductive film and that application of a voltage to the conductive film is carried out in reduced atmosphere or that the two types of metal elements are Pd and Pt or that an atomisity composition of the Pt is not more than 50 atomic %.
In addition, the present invention provides a method for manufacturing an electron source having a plurality of electron emitting devices, wherein the electron emitting device is manufactured by any one of the above-described methods.
Additionally, the present invention provides a method for manufacturing an electron source having a plurality of electron emitting devices matrix-wired on a substrate, wherein the electron emitting device is manufactured by any one of the above-mentioned methods.
Moreover, the present invention provides a method for manufacturing an image forming apparatus comprising an electron source and an image forming member for forming an image by irradiation of an electron ray from the electron source, wherein the electron source is manufactured by any one of the above-mentioned methods.